The large animal is considered an imminent threat to public safety by Fontana police

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A volunteer with the Fontana Police Department distributes information about a mountain lion that killed a 100-pound German Shepherd Wednesday March 4, 2014.

A mountain lion exhibited behavior considered "anything but normal" when it attacked and killed a 100-pound German Shepherd before standing its ground when the dog's owner and officers encountered the animal in the back yard of Southern California home.

Fontana police are urging residents to keep pets inside careful after the dog's death early Wednesday. The mountain lion is considered a "significant public safety threat," meaning it cannot be relocated, police said.

Police responded after the dog’s owner went to his backyard and found the mountain lion standing over his deceased pet. The mountain lion hopped a brick wall to enter the property, part of what authorities described as a pattern of unsual behavior in an area where reports of mountain lion sightings are common.

"What was unique was the behavior of this mountain lion," said Fontana Police Chief Rodney Jones, adding that officials with the California DFW described the behavior as "very bizarre and very unique."

After hearing the attack, the homeowner went outside and turned on a light.

"Normally, they do not like to be around people, and they do not like the lights," Jones said. "This mountain lion stood its ground by growling at him and getting ready to jump on him.

"As officers arrived, a couple of officers got within 10 to 15 feet. The mountain lion was in a position where could pounce on an officer."

Officers retreated and fired several rounds, initially scaring it into a nearby canyon. The large cat returned four more times before eventually disappearing.

There is no evidence the lion was struck by any rounds, officials said.

The Fontana Police Department has deemed the mountain lion a threat to public safety and is working with Fish and Wildlife officials to track the animal. Residents are being warned to avoid hiking or jogging around dawn, dusk, and at night when the animals are most active and to keep pets inside.

An animal is considered a public safety threat if there is "a likelihood of human injury based on the totality of the circumstances," according to the California Department of Fish and Wildlife. The lion's behavior, proximity to schools and other factors are considered in making that determination.

DFW agents and police have been deployed in the neighborhood. A helicopter with infrared sensors that allow for improved searching capability at night was assigned to the area.

Volunteers have been distributing information about the animal to residents.